<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    function f(n) {
        if (n === 1) {
            return 1
        } else if (n === 2) {
            return 2
        }
        else {
            return f(n - 1) + f(n - 2)
        }
    }


</script>
</body>
</html>